The present invention relates to a stapler for driving staples into objects, such as sheaves of papers, said stapler comprising an anvil element, which has a means for clinching driven-in staples, and a stapling element, which cooperates with the anvil element and which contains staples, one of the anvil element and the stapling element being fixedly arranged in the stapler, and these elements being movable relative to each other between a starting position and a working position, in which they are applied against an object, when this is placed in the stapler between the anvil element and the stapling element to be stapled, and said stapler further comprising a driver, which is reciprocatingly arranged on the stapling element and which is arranged to drive a staple into the object in the direction of the anvil element, and an operating element, which is arranged to reciprocate the driver and which, for this purpose, is movable relative to the stapling element; the anvil element and the operating element being movable back and forth relative to the stapling element in one and the same path of motion, and the anvil element and the operating element being movable relative to each other in said path of motion with the aid of a reversible driving means.
In a conventional stapler, the anvil element is attached to a fixed base and the stapling element is pivotally connected to the base on a first axis in order to be pivoted, for instance when a sheaf of papers is placed on the anvil element, towards said anvil element and be applied against the sheaf of papers. The operating element has two arms, which are pivotally connected to the stapling element on an axis parallel to the first axis in order to be pivoted, when the stapling element is in its working position and is applied against the sheaf of papers, in the direction of the base, thus driving a staple into the object. As should be understood, the working position of the stapling element, i.e. the position in which the stapling element is applied against the sheaf of papers and presses the same against the anvil element, depends on the thickness of the sheaf of papers. To compensate for these variations in the thickness of the sheaf and to guide and drive the stapling element and the operating element in such a manner that it will be possible to staple sheaves of papers of varying thickness in a reliable manner, use is made today of different types of cam controls, locking mechanisms and spring arrangements, resulting in the stapler containing many parts and being unwieldy and expensive.
Therefore the object of the present invention is to provide a simple and compact stapler, which makes it possible to provide, in a simple manner, an automatic compensation for varying thickness of the objects which are to be stapled.
According to the invention, this object is achieved by a stapler, which is of the kind stated by way of introduction and characterised in
that the operating element is movably connected to the stapling element and the anvil element in such a manner that its inertia against movement relative to the stapling element is greater than its inertia against movement relative to the anvil element, which means that, when the driving means is driven in one direction, the anvil element and the stapling element are first moved relative to each other from the starting position to the working position and the operating element is subsequently moved relative to the stapling element to move the driver in its drive-in direction, and that, when the driving means after reversal is driven in the other direction, the anvil element and the stapling element are first moved relative to each other from the working position to the starting position and the operating element is subsequently moved relative to the stapling element in order to move the driver in the direction opposite to the drive-in direction, and
that the driving means is adapted to be reversed, on the one hand, when the operating element, when driving the driving means in said one direction, reaches a first position, in which it cannot move the driver any further in its drive-in direction and, on the other hand, when the operating element, when driving the driving means in said other direction, reaches a second position, in which it cannot move the driver any further in the direction opposite to the drive-in direction.
The driving means advantageously comprises a reversible electric motor, and the rise of current which is obtained in the motor when it stalls due to the operating element being stopped in its movement in said first and second position is used as a signal to reverse the motor.
In a first preferred embodiment, the anvil element and the operating element are linearly movable, along one and the same straight line, back and forth relative to the stapling element. The electric motor is suitably fixed to one of the operating element and the anvil element. If in this first preferred embodiment the stapling element is fixedly arranged in the stapler, the anvil element, the stapling element and the operating element are suitably arranged in a vertical line and movable relative to each other along this line, the anvil element being arranged above the stapling element. If in the first preferred embodiment the anvil element is fixedly arranged in the stapler, the anvil element, the stapling element and the operating element are suitably arranged in a vertical line and movable relative to each other along this line, the stapling element being arranged above the anvil element.
In the first preferred embodiment, the driving means suitably comprises at least one gear, which meshes with a rack that is fixed to the other one of the operating element and the anvil element.
In a second preferred embodiment, the anvil element and the operating element are pivotable back and forth relative to the stapling element on one and the same axis. If in the second preferred embodiment the stapling element is fixedly arranged in the stapler, the anvil element is suitably arranged above the stapling element. If in the second preferred embodiment the anvil element is fixedly arranged in the stapler, the stapling element is suitably arranged above the anvil element.